How do you buy weapons on combat arms?

In order to purchase weapons, first join a channel. On the top of your screen, you will see "Shop/Storage". In there, it will show your weapons. Then, towards the top right corner, you will see a SHOP. Click on that and it will show weapons. Then, click a weapon and toward the bottom right corner, you will see BUY. A square will come up and it will show an option on how long you wish to have the weapon. Choose you time and follow the steps it shows you, and you have yourself a weapon for a certain period of time.

Combat Arms - Nexon Games